Cleveland Park resident Aurora Ferrari spent two years designing and constructing DC's first net-zero accessory dwelling unit. Stone walls left over from a 1920s garage were incorporated into the design. In the spring of 2020, Aurora Ferrari looked at the plot of land sandwiched between her D.C. backyard and an alley, and saw potential.
After putting the structure through a rigorous energy evaluation, the city determined last year that it did indeed qualify as the first net-zero ADU within the District. The achievement didn’t come easy. It took the better part of two years to come to fruition, including around nine months to obtain the necessary permits and roughly seven months to actually construct it. Ferrari says the project ran about $330 per square foot, or about $200,000 in all.
While Ferrari was working on the design, she focused on ensuring “the suppliers I was using were friendly to the environment,” paying particular attention to companies that employed solar energy and didn’t use plastic wrapping to ship their goods. She also favored products made of recycled materials, such asThe more extreme the climate, the more energy it takes to keep the home comfortable. In D.C.
Ferrari’s ADU has double the insulation of a typical structure — the exterior is insulated with foam board, the interior walls with spray foam. She also used a membrane sourced from Germany to help seal the structure and protect the inner workings from moisture.Another, more straightforward part of making a building airtight is eliminating unnecessary holes in the exterior.